Why Two Advisors Sell the Same Part (And How to Stop It)

Somebody is getting the phone call.

On Monday an advisor books a cambelt for Tuesday morning, checks the shelf, sees the kit, promises the car back by two. On Monday afternoon a different advisor books another cambelt for Wednesday, checks the same shelf, sees the same kit, makes the same promise.

There was one kit. There are now two promises. On Tuesday afternoon somebody works out which customer gets rung, and the answer is usually whoever is least likely to complain, which is a poor basis on which to run a workshop.

Everyone who has worked a service desk knows this one. It is worth looking at properly, because the cause is not carelessness and the fix is not a bigger whiteboard.

The shelf is not the question

Both advisors did their job. They checked, the part was there, they committed.

The problem is that "is it there" is the wrong question. What an advisor actually needs to know is "is it there and is it still mine to promise", and a shelf cannot answer the second half. Nor can a spreadsheet that says eleven, nor a stock figure in a system that only counts what is physically present.

A promise to a customer is a claim on that part. From the moment it is made, that kit is no longer available to anyone else, even though it is still sitting in the rack where anyone can see it. Until your stock figure understands that, the shelf will keep lying to the second advisor, politely and in good faith.

Reserved, not just counted

The fix is one idea: when a part goes onto a job card, it is reserved for that job.

Which means three numbers rather than one:

On hand. What is physically in the building. Eleven.

Reserved. What is already promised to jobs that have not been completed yet. Four.

Available. What is genuinely free for the next advisor to commit. Seven.

The third number is the only one anybody should be looking at when they make a promise, and it is the one that does not exist in most workshops.

Go back to the cambelt. Monday morning, the advisor adds the kit to the Tuesday job. On hand stays at one, because the kit has not moved. Available drops to zero. Monday afternoon, the second advisor opens the part and sees nothing free. No phone call on Tuesday, because the conversation happened on Monday when it was cheap, and the second customer was booked for Thursday instead.

That is it. That is the entire mechanism. It does not require the technician to do anything, it does not require a stores man, and it happens because an advisor did what they were already doing.

The bit that matters on a busy Monday

Two advisors on the phone at the same moment, one unit left, both clicking add.

This is where a naive system fails, and fails in the worst possible way, because it says yes to both and nobody finds out until Tuesday. In Vehiso the reservation is taken under a lock on that stock record, which in plain terms means the two requests are made to queue. One gets the kit. The other is told, on screen, immediately, that there is none free.

It is an unglamorous detail and it is the difference between a stock figure you can trust and one you cannot. A number that is right except when two people are busy at once is a number that is wrong exactly when it matters.

When there genuinely is not one

Reserving only helps if the workshop does something sensible when the shelf cannot cover the job. Two advisors, two customers, one kit: somebody still needs a part.

So a line that cannot be fully covered moves the job to Awaiting parts. Not a note in a comment box that one person sees. A status on the job, visible to whoever is planning the week, that says this car cannot be worked on yet and here is the reason.

When the delivery arrives and is booked in, the job is topped up and, if nothing else is short, the status clears on its own. Nobody has to remember which job was waiting on what. We wrote that up separately in the part arrived on Thursday and the job did not know.

Where the stock actually goes

Worth being precise about the moment stock leaves, because it is not when the part is promised.

Reserving does not reduce what is on hand. The kit is still in the rack, and if the job is cancelled on Tuesday morning the reservation goes with it and the kit is free again. The stock is issued when the job is completed, which is also the moment the cost is stamped onto the line so your margin on that job cannot move afterwards. That distinction is worth a post of its own, and it has one: what a part costs is not what you paid for it.

The practical version: reserved means spoken for, issued means gone, and the difference between them is where double-booking lives.

What this looks like for the people doing the work

The advisor sees one number, available, and can promise against it without walking to the rack.

The technician sees the parts on the job and where they live on the shelf. They are not asked to manage stock, they are asked to stop hunting.

Whoever runs the parts desk, if anyone does, gets a movement history where every change names the job, the delivery or the count behind it. That is the subject of eleven on the system, seven on the shelf.

One honest limitation. By default the system will not let stock go negative, because negative stock is almost always a mistake rather than a fact. A branch that genuinely needs to work that way can turn it on, but we would ask why first.

If you hold no stock at all

Then none of this applies to you, and that is fine. Reservation is machinery for workshops with something on the shelf to reserve.

If you buy every part per job from a factor, the part of the module worth switching on is much smaller and it is covered in you do not need a stores man to know what parts make you. Two fields on a job card line and you have your parts margin.